One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,5)(7,8)(9,10,12,14)(11,15,16,13)(17,18)(19,21)(20,22)(23,24)(26,30)(27,33)(32,39)(35,37)(2,5)(6,8)(17,19,20,23)(18,21,22,24)(25,26,29,32,28,30,36,39)(27,34,35,38,33,40,37,31)(3,7)(6,8)(9,11,12,16)(10,13,14,15)(25,27,28,33)(26,31,30,38)(29,37,36,35)(32,40,39,34)(1,3,4,7)(2,6,5,8)(18,22)(21,24)(27,33)(31,38)(34,40)(35,37)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.